1. Field of the Invention
The present invention relates to a side curtain air bag arranged to deploy along the side of a vehicle to protect occupants during a crash involving the vehicle, including a rollover. The side curtain air bag may even wrap around a front-seated occupant, i.e., have a frontal portion designed to deploy between a front-seated occupant and the dashboard.
The present invention also relates to an air bag having a number of interconnected compartments for use in vehicular crashes whereby the air bag deploys before or during the crash to cushion the occupant of the vehicle and prevent injury to the occupant. The invention also relates to a method for making an air bag having interconnected compartments and an occupant protection system including an air bag with interconnected compartments.
The present invention also relates to a vehicular air bag having a low mass and made substantially from thin plastic film which is designed to deploy in a collision involving the vehicle so that if it impacts the occupant of the vehicle wherever he/she is located, it will not cause significant injury to the occupant. In order to make a film air bag of sufficiently low mass so as not to injure the occupant, it has been recognized that the film air bag must contain means to arrest the propagation of a tear so that a small hole or break in the film does not result in a catastrophic failure, i.e., cause the air bag to burst like a balloon or otherwise prevent the air bag from deploying properly. One particular method of arresting the propagation of a tear of this invention is to use a combination of an elastomeric film and reinforcement means which in certain embodiments may be the elastomeric material itself constructed in a variable thickness pattern, i.e., have thinner and thicker sections, or in a manner so that it has strategically placed thicker sections, i.e., relative to remaining portions of the material, in view of stress considerations during deployment.
2. Description of Prior Art
A conventional driver side air bag (also referred to herein as a driver air bag) is made from pieces of either Nylon or polyester fabric that are joined together, e.g., by sewing. The air bag is usually coated on the inside with neoprene or silicone for the purposes of (i) capturing hot particles emitted by the inflator in order to prevent holes from being burned in the fabric, and (ii) sealing the air bag to minimize the leakage of an inflating gas through the fabric. These air bags are conventionally made by first cutting two approximately circular sections of a material having a coating on only one side and which will form a front panel and a back panel, and sewing them together with the coated side facing out. The back panel is provided with a hole for attachment to an inflator. Fabric straps, called tethers, are then sewn to the front panel. Afterwards, the air bag is turned inside out by pulling the fabric assembly through the inflator attachment hole placing the coated side on the inside. Assembly is completed by sewing the tethers to the back panel adjacent the inflator attachment hole.
If a conventional driver air bag is inflated without the use of tethers, the air bag will usually take an approximately spherical shape. Such an inflated air bag would protrude significantly into the passenger compartment from the steering wheel and, in most cases, impact and injure the driver. To prevent this possible injury, the tethers are attached to the front and rear panels of the air bag to restrict the displacement of the front panel relative to the back panel. The result of the addition of such tethers is an air bag that has the shape of a flat ellipsoid with a ratio of the thickness of the air bag to its diameter of approximately 0.6. In the conventional air bag, the tethers are needed since the threads that make up the air bag fabric are capable of moving slightly relative to each other. The air bag is elastic for stresses that are not aligned with the warp or woof of the fabric. As a result, the fabric would distort to form an approximate sphere in the absence of such tethers.
Moreover, the above-mentioned method of manufacturing an air bag involves a great deal of sewing and thus is highly labor intensive and, as a result, a large percentage of all driver air bags are presently manufactured in low labor cost countries such as Mexico.
Many people are now being injured and some killed by interaction with the deploying air bag (See, e.g., xe2x80x9cWarning: Too Much Safety May Be Hazardousxe2x80x9d, New York Times, Sunday, Dec. 10, 1995, Section F, Page 8). One of the key advantages of the film air bag described in the current assignee""s above-referenced patents and patent applications is that, because of its much lower mass than conventional Nylon or polyester fabric air bags, the injury caused by this interaction with the deploying air bag is substantially reduced. In accordance with the teachings of those patents and patent applications mentioned above, the driver air bag system can be designed to permit significant interaction with the driver. In other words, the film air bag can be safely designed to intrude substantially further into the passenger compartment without fear of injuring the driver. Nevertheless, in some cases, as described in U.S. Pat. No. 5,653,464, it may be desirable to combine the properties of a film air bag, which automatically attains the conventional driver air bag shape, with a fabric air bag. In such cases, interaction with the driver needs to be minimized.
Air bag systems today are designed so that ideally the air bag is fully inflated before the occupant moves into the space that is occupied by the air bag. However, most occupants are not positioned at the ideal location assumed by the air bag system designer, and also may not have the dimensions, e.g., size and weight, in the range considered for optimum air bag deployment by the air bag system designer. Many occupants sit very close to the air bags, or at least closer than expected by the air bag system designer, and as mentioned above, are injured by the air bag deployment. On the other hand, others sit far from the air bag, or at least farther away from the air bag than expected, and therefore must travel some distance, achieving a significant relative velocity, before receiving the benefit of the air bag. See for example xe2x80x9cHow People Sit in Cars: Implications For Driver and Passenger Safety in Frontal Collisionsxe2x80x94The Case for Smart Restraints.xe2x80x9d, Cullen, E., et al 40th Annual Proceedings, Association For the Advancement of Automotive Medicine, pp. 77-91.
With conventionally mounted air bags such as those mounted in the steering wheel or instrument panel, severe out-of-position occupant situations, where the occupant is resting against the air bag when deployment begins, can probably only be handled using an occupant position sensor, such as disclosed in the current assignee""s U.S. Pat. No. 5,653,462 (corresponding to published WO 94/22693), which is incorporated herein by reference, which prevents an air bag from deploying if an occupant is more likely to be seriously injured by the air bag deployment than from the accident itself. In many less severe accidents, the occupant will still interact with the deploying air bag and sustain injuries ranging from the mild to the severe. In addition, as mentioned above, some occupants sit very far from the steering wheel or instrument panel and, with conventional air bags, a significant distance remains between the occupant and the inflated air bag. Such occupants can attain a significant kinetic energy relative to the air bag before impacting it, which must be absorbed by the air bag. This effect serves to both increase the design strength requirements of the air bag and increase the injury induced in the occupant by the air bag. For these reasons, it would be desirable to have an air bag system that adjusts to the location of the occupant and which is designed so that the impact of the air bag causes little or no injury to the occupant.
It is conventional in the art that air bags contain orifices or vent holes for exhausting or venting the gas generated by the inflation means. Thus, typically within one second after the bag is inflated (and has provided its impact absorbing function), the gas has been completely exhausted from the bag through the vent holes. This imposes several limitations on the restraint system that encompasses the air bag system. Take for example the case where an occupant is wearing a seatbelt and has a marginal accident, such as hitting a small tree, which is sufficient to deploy the air bag, but where it is not really needed since the driver is being restrained by his seatbelt. If the driver has lost control of the car and is traveling at 30 MPH, for example, and has a secondary impact one second or about 50 feet later, this time with a large tree, the air bag will have become deflated and thus is not available to protect the occupant in this secondary life threatening impact.
In other situations, the occupant might be involved in an accident that exceeds the design capability of the restraint system. These systems are typically designed to protect an average-size male occupant in a 30-MPH barrier impact. At higher velocities, the maximum chest deceleration experienced by the occupant can exceed 60 G""s and become life threatening. This is particularly a problem in smaller vehicles, where air bag systems typically only marginally meet the 60-G maximum requirement, or with larger or more frail occupants.
There are many cases, particularly in marginal crashes, where existing crash sensors will cause the air bag to deploy late in the crash. This can also result in an xe2x80x9cout-of-position occupantxe2x80x9d for deployment of the air bag that can cause injuries and possibly death to the occupant. Other cases of out-of-position occupants are standing children or the forward motion of occupants during panic braking prior to impact especially when they are not wearing seatbelts. The deploying air bag in these situations can cause injury or death to the out-of-position occupant. Approximately one hundred people have now been killed and countless more seriously injured by the deployment of the air bag due to being out-of-position.
It is recognized in the art that the air bag must be available to protect an occupant for at least the first 100-200 milliseconds of the crash. Since the air bag contains large vents, the inflator must continue to supply gas to the air bag to replace the gas flowing out of these vents. As a result, inflators are usually designed to produce about twice as much gas than is needed to fill the air bag. This, of course, increases the cost of the air bag system as well as its size, weight and total amount of contaminants resulting from the gases that are exhausted into the automobile environment.
This problem is compounded when the air bag becomes larger, which is now possible using the film materials of this invention, so as to impact with the occupant wherever he/she is sitting, without causing significant injury, as in the preferred implementation of the design of this invention. This then requires an even larger inflator which, in many cases, cannot be accommodated in conjunction with the steering wheel, if conventional inflator technology is utilized.
Furthermore, there is a great deal of concern today for the safety of a child in a rear facing child seat when it is used in the front passenger seat of a passenger air bag equipped vehicle. Currently used passenger side air bags have sufficient force to cause significant injury to a child sitting in such a seat and parents are warned not to use child seats in the front seat of a vehicle having a passenger side air bag. Additionally, several automobile companies are now experimenting with rear seat air bags in which case, the child seat problem would be compounded.
Air bags made of plastic film are disclosed in the patents and patent applications referenced above. Many films have the property that they are quite inelastic under typical stresses associated with an air bag deployment. If an air bag is made from a pair of joined flat circular sections of such films and inflated, instead of forming a spherical shape, it automatically forms the flat ellipsoidal shape required for driver air bags as described in U.S. Pat. No. 5,653,464. This unexpected result vastly simplifies the manufacturing process for driver air bags since tethers are not required, i.e., the film air bag is made from two pieces of film connected only at their peripheral edges. Furthermore, since the air bag can be made by heat-sealing two flat circular sections together at their peripheral edges without the need for tethers, the entire air bag can be made without sewing, reducing labor and production costs. In fact, the removal of the requirement for tethers permits the air bag to be made by a blow molding or similar process. Indeed, this greatly reduces the cost of manufacturing driver air bags. Thus, the use of film for making an air bag has many advantages that are not obvious.
Films having this inelastic quality, that is films with a high modulus of elasticity and low elongation at failure, tend to propagate tears easily and thus when used alone are not suitable for air bags. This problem can be solved through the addition of reinforcement in conjunction with the inelastic films such as a net material as described in the above-referenced patents and patent applications. Other more elastic films such as those made from the thermoplastic elastomers, on the other hand, have a low modulus of elasticity and large elongation at failure, sometimes 100%, 200% or even 400%, and naturally resist the propagation of tears. Such films, on the other hand, do not form the flat ellipsoidal shape desired for steering wheel-mounted driver side air bags. As discussed in greater detail below, the combination of the two types of film through attachment using lamination, successive casting or coating, or through the use of adhesives applied in a pattern can produce a material having both the self shaping and the resistance to tear propagation properties.
In addition to the above-referenced patents and patent applications, film material for use in making air bags is described in U.S. Pat. No. 4,963,412 to Kokeguchi, which is incorporated herein by reference. The film air bag material described in the Kokeguchi patent is considerably different in concept from that disclosed in the above-referenced patents and patent applications or the instant invention. The prime feature of the Kokeguchi patent is that the edge tear resistance, or notch tear resistance, of the air bag film material can be increased through the use of holes in the plastic films, i.e., the film is perforated. Adding holes, however, reduces the tensile strength of the material by a factor of two or more due to the stress concentration effects of the hole. It also reduces the amount of available material to resist the stress. As such, it is noteworthy that the Kokeguchi steering wheel mounted air bag is only slightly thinner than the conventional driver side fabric air bag (320 micrometers vs. the conventional 400 micrometers) and is likely to be as heavy or perhaps heavier than the conventional air bag. Also, Kokeguchi does not disclose any particular shapes of film air bags or even the air bag itself for that matter. Since his air bag has no significant weight advantage over conventional air bags, there is no teaching in Kokeguchi of perhaps the most important advantage of film air bags of the present invention, that is, in reducing injuries to occupants who interact with a deploying air bag.
As discussed in detail below, the air bags constructed in accordance with the present teachings attain particular shapes based on the use of the inelastic properties of particular film materials and reduce tear propagation through a variety of novel methods including the use of elastic films. It is also noteworthy that Kokeguchi discloses that vacuum methods can be used to form the air bag into the desired shape and thus fails to realize that the properties of inelastic film results in the air bag automatically forming the correct shape upon deployment. Also noteworthy is that Kokeguchi states that polymeric films do not have sufficient edge tear resistance and thus fails to realize that films can be so formulated to have this property, particularly those made from the thermoplastic elastomers. These limitations of the Kokeguchi patent results in a very thick air bag that although comprised of film layers no longer qualifies as a true film air bag as defined herein. A xe2x80x9cfilm air bagxe2x80x9d for the purposes herein is one wherein the film thickness is generally less than about 250 micrometers, and preferably even below about 100 micrometers, for use as a driver protection air bag. As the size of the air bag increases, the thickness must also increase in order to maintain an acceptable stress within the film. A film air bag so defined may also contain one or more sections that are thicker than about 250 micrometers and which are used primarily to reinforce the thinner film portion(s) of the air bag. A film air bag as defined herein may also include a layer or layers of inelastic material and a layer or layers of elastic material (i.e., thermoplastic elastomers).
The neoprene or silicone coating on conventional driver air bags, as mentioned above, serves to trap hot particles that are emitted from some inflators, such as a conventional sodium azide inflator. A film air bag may be vulnerable to such particles, depending on its design, and as a result cleaner inflators that emit fewer particles are preferred over sodium azide inflators. It is noteworthy, however, that even if a hole is burned through the film by a hot particle, the use of an thermoplastic elastomer in the film material prevents this hole from propagating and causing the air bag to fail. Also, new inflators using pyrotechnic, hybrid or stored gas technologies, are now available which do not produce hot particles and produce gases which are substantially cooler than gases produced by sodium azide inflators. Also, not all sodium azide inflators produce significant quantities of hot particles.
One interesting point that also is not widely appreciated by those skilled in the art heretofore, is that the gas temperature from the inflator is only an issue in the choice of air bag materials during the initial stages of the inflation. The total thermal energy of the gas in an air bag is, to a first order approximation, independent of the gas temperature which can be shown by application of the ideal gas laws. When the gas initially impinges on the air bag material during the early stages of the inflation process, the temperature is important and, if it is high, care must be taken to protect the material from the gas. Also, the temperature of the gas in the air bag is important if the vent holes are located where the out-flowing gas can impinge on an occupant. The average temperature of the air bag itself, however, will not be affected significantly by the temperature of the gas in the air bag.
In certain conventional air bag deployments, the propellant which is used to inflate the air bag also is used to force open a hole in the vehicle trim, called the deployment door, permitting the air bag to deploy. Since the mass of a film air bag is substantially less than the mass of a conventional fabric air bag, much less energy is required to deploy the air bag in time. However, substantial pressure is still required to open the deployment door. Also, if the pressure now used to open the deployment door is used with film air bags, the air bag velocity once the door has been opened may be substantially higher than conventional air bags. This rapid deployment can put excessive stresses on the film air bag and increases the chance that the occupant will be injured thereby. For most implementations of the film air bag, an alternate less energetic method of opening the deployment door may be required.
One such system is described in Barnes et al. (U.S. Pat. No. 5,390,950) entitled xe2x80x9cMethod and arrangement for forming an air bag deployment opening in an auto interior trim piecexe2x80x9d. This patent describes a method xe2x80x9c . . . of forming an air bag deployment opening in an interior trim piece having a vinyl skin overlying a rigid substrate so as to be invisible prior to operation of the air bag system comprising an energy generating linear cutting element arranged in a door pattern beneath the skin acting to degrade or cut the skin when activated.xe2x80x9d
The goal of the Barnes et al. patent is to create an invisible seam when the deployment door is located in a visible interior trim panel. This permits greater freedom for the vehicle interior designer to create the particular aesthetic effect that he or she desires. The invisible seam of the Barnes et al. patent is thus created for aesthetic purposes with no thought toward any advantages it might have to reduce occupant injury or advantages for use with a film air bag, or to reduce injuries at all for that matter. One unexpected result of applying the teachings of this patent is that the pressure required to open the deployment door, resulting from the force of the inflating air bag, is substantially reduced. When used in conjunction with a film air bag, this result is important since the inflator can be designed to provide only sufficient energy to deploy and inflate the very light film air bag thereby significantly reducing the size of the inflator. The additional energy required to open a conventional deployment door, above that required to open a deployment door constructed in accordance with the teachings of the Barnes et al. patent, is not required to be generated by the inflator. Furthermore, since a film air bag is more vulnerable to being injured by ragged edges on the deployment door than a conventional fabric air bag, the device of the Barnes et al. patent can be used to pyrotechnically cut open the deployment door permitting it to be easily displaced from the path of the deploying air bag, minimizing the force of the air bag against the door and thus minimizing the risk of damage to the film air bag from the deployment door. Since Barnes et al. did not contemplate a film air bag, advantages of its use with the pyrotechnically opening deployment door could not have been foreseen. Although the Barnes et al. patent discloses one deployment door opening method which is suitable for use with an air bag made from plastic film as disclosed herein, that is one which requires substantially less force or pressure to open than conventional deployment doors, other methods can be used in accordance with the invention without deviating from the scope and spirit thereof.
The discussion of the self-shaping air bag thus far has been limited to film air bags. An alternate approach is to make an air bag from a combination of fabric and film. The fabric provides the tear resistance and conventional air bag appearance. The film forces the air bag to acquire the flat ellipsoidal shape desired for driver air bags without the use of tethers and permits the air bag to be assembled without sewing using heat and/or adhesive sealing techniques. Such a hybrid air bag is made from fabric and film that have been laminated together prior to the cutting operation. Naturally, the combination of a film and net, as described in the above referenced patents and patent applications, is equally applicable for the air bag described here and both will be referred to herein as hybrid air bags and belong to the class of composite air bags.
A finite element analysis of conventional driver side air bags (made of fabric) shows that the distribution of stresses is highly unequal. Substantial improvements in conventional air bag designs can be made by redesigning the fabric panels so that the stresses are more equalized. Today, conventional air bags are designed based on the strength required to support the maximum stress regardless of where that stress occurs. The entire air bag must then be made of the same thickness material as that chosen to withstand maximum stress condition. Naturally, this is wasteful of material and attempts have been made to redesign the air bag to optimize its design in order to more closely equalize the stress distribution and permit a reduction in fabric strength and thus thickness and weight. However, this optimization process when used with conventional fabric air bags can lead to more complicated assembly and sewing operations and more expensive woven materials and thus higher overall manufacturing costs. An example of such an air bag is that marketed by Precision Fabrics of Greensboro, N.C. Thus, there is a tradeoff between manufacturing cost and air bag optimization.
As discussed in the above-referenced patents and patent applications as well as below, with a film air bag manufactured using blow molding techniques, for example, greater freedom is permitted to optimize the air bag vis-à-vis equalization of the stress. First, other than tooling cost, the manufacturing cost of an optimized air bag is no greater than for a non-optimized air bag. Furthermore, the thickness of the film can be varied from one part of the air bag to another to permit the air bag to be thicker where the stresses are greater and thinner where the stresses are less. A further advantage of blow molding is that the film can be made of a single constituent material. When the air bag is fabricated from sheet material, the outside layer of the material needs to be heat sealable, such as is the case with polyethylene or other polyolefin, or else a special adhesive layer is required where the sealing occurs.
As discussed in greater detail below in connection with the description of the invention, when the film for the air bag is manufactured by casting or coating methods, techniques familiar to those skilled in the art of plastics manufacturing are also available to produce a film where the thickness varies from one part to another in a predetermined pattern. This permits a film to be made that incorporates thicker sections in the form of a lattice, for example, which are joined together with thin film. Thus, the film can be designed so that reinforcing ribs, for example, are placed at the optimum locations determined by mathematical stress analysis.
One example of an inflatable film product which partially illustrates the self-shaping technology of this invention is the common balloon made from metalized xe2x80x9cMylarxe2x80x9d(trademark) plastic film found in many stores. Frequently these balloons are filled with helium. They are made by heat-sealing two flat pieces of film together as described in U.S. Pat. Nos. 5,188,558 (Barton), 5,248,275 (McGrath), 5,279,873 (Oike), and 5,295,892 (Felton). Surprisingly, the shape of these balloons, which is circular in one plane and elliptical in the other two planes, is very nearly the shape which is desired for a driver side air bag. This shape is created when the pressure within the balloon is sufficiently low such that the stresses induced into the film are much smaller than the stresses needed to significantly stretch the film. The film used is relatively rigid and has difficulty adjusting to form a spherical shape. In contrast, the same air bag made from woven material more easily assumes an approximate spherical shape requiring the use of tethers to create the shape which comes naturally with the Mylar balloons.
One problem with film balloons is that when a hole is punctured in the balloon it fails catastrophically. One solution to this problem is to use the combination of a film and net as described in the current assignee""s above-referenced patents and patent applications. Such materials have been perfected for use as sail material for lightweight high performance sails for sailboats. One example is marketed under the trade name Bainbridge Sailcloth SL Series(trademark), and in particular SL 500-P(trademark), 1.5 mill. This material is a laminate of a film and a net. Such materials are frequently designed to permit heat-sealing thereby eliminating threads and the stress concentrations associated therewith. Heat-sealing also simplifies the manufacturing process for making sails. Another preferable solution is to make the air bags from a film material which naturally resists tears, that is, one which is chemically formulated to arrest a tear which begins from a hole, for example. Examples of films which exhibit this property are those from the thermoplastic elastomer (TPE) families such as polyurethane, Ecdel elastomer from Eastmen, polyester elastomers such as HYTREL(trademark) and some metallocene catalyzed polyolefins. For the purposes herein, a thermoplastic elastomer will include all plastic films which have a relatively low modulus of elasticity and high elongation at failure, including but not limited to those listed above.
Applications for the self shaping air bag described herein include all air bags within the vehicle which would otherwise required tethers or complicated manufacturing from several separate panels. Most of these applications are more difficult to solve or unsolvable using conventional sewing technology. The invention described herein solves some of the above problems by using the inelastic properties of film, and others by using the elastic properties of thermoplastic elastomers plus innovative designs based on analysis including mathematical modeling plus experimentation. In this manner, the problems discussed above, as well as many others, are alleviated or solved by the air bags described in the paragraphs below. Films for air bags which exhibit both the self-shaping property and also formulated to resist the propagation of a tear are made by combining a layer of high modulus material with a layer of a thermoplastic elastomer. Then if a tear begins in the combined film it will be prevented from propagating by the elastomer yet the air bag will take the proper shape due to the self-shaping effect of the high modulus film.
Other relevant prior art includes the following, with a brief explanation of the pertinence of the reference to the present invention:
U.S. Pat. No. 3,511,519 (Martin) describes a large fabric air bag which is shown impacting the occupant. It does not discuss the problem of injury to the occupants due to the impact of the air bag.
U.S. Pat. No. 3,573,885 (Brawn) shows a blowout patch assembly but not variable exhaust orifices.
U.S. Pat. No. 3,820,814 (Allgaier) discloses variable exhaust vents located within the fabric air bag material.
U.S. Pat. No. 3,888,504 (Bonn) illustrates an inflatable occupant restraint air bag which is comprised at least in part of a woven stretch fabric which is permeable to fluid used to inflate the bag, the bag having a variable porosity which increases and decreases in relation to the fluid pressure within the bag.
U.S. Pat. No. 4,262,931 (Strasser) illustrates two air bags joined together to cover right and center seating positions.
U.S. Pat. No. 4,360,223 (Kirchoff) discloses a low-mount, air bag module for the passenger side of an automobile that uses two bags that are folded within a housing that is open at one end. One of the bags is for restraining the knees of the passenger to prevent forward sliding in the event of a crash, the other bag being for restraining the torso. The knee bag is inside the torso bag and they are both attached directly to the inflator, the knee bag being arranged to be inflated first. The torso bag then is inflated to prevent forward rotation of the passenger from the hips.
Further, in accordance with the Kirchoff invention, a pressure responsive orifice means is provided in a second opening in the wall of the knee bag. This orifice means controls the flow of gas through the opening in the wall of the knee bag thereby to insure a predetermined gas pressure within the knee bag, while permitting subsequent inflation of the torso bag by gases passing into the torso bag through the orifice means. Thus, a knee bolster air bag is described but it is positioned inside of the main torso air bag and inflated by the same inflator.
U.S. Pat. No. 4,394,033 (Goetz) discloses a temperature compensation system. The claimed inflatable occupant-restraint system in a vehicle includes a generator for producing fluid under pressure placed such that a portion of the generator is outside the cushion and has a resilient venting means for dumping increasing fractions of gas volume outside the cushion at increasing operating temperatures.
U.S. Pat. No. 4,805,930 (Takada) discloses a temperature compensation system. Further, it describes stitched thread seams between fabric elements of the envelope of a vehicle safety air bag which induce localized distension and opening up of the envelope fabrics along the seams, thereby causing the film coatings of the envelope fabric to rupture along the seam and allow gas to escape and maintain a substantially constant overall maximum pressure, regardless of variations in ambient temperature.
U.S. Pat. No. 3,451,693 (Carey) does not disclose plastic film, merely plastic. The distinguishable properties of film are numerically described in the instant specification and basically are thinner and less weight. Carey does disclose variable exhaust orifice means at col. 3, lines 63+ to maintain constant pressure in the air bag as the occupant is thrown into the air bag. However, the material is not plastic film with means to arrest the propagation of a tear. In fact, it is unclear in Carey as to whether the orifice means therein is repeatable/reusable and no mention is made as to whether the stretching of the orifice means area is permanent or temporary.
U.S. Pat. No. 3,638,755 (Sack) discloses a two-bag air bag combination, with one bag contained within the other.
U.S. Pat. No. 3,675,942 (Huber) discloses a unidirectional valve which permits air to enter the bag, but prevents its escape in the event the pressure within the bag exceeds that of the atmosphere within the vehicle, such as by the impact of a person with the bag.
U.S. Pat. No. 3,752,501 (Daniel) discloses an inflatable cushion device for protective interposition between a vehicle operator and the rim and hub of a vehicle steering wheel assembly. The cushion is compartmented to provide, when inflated, peripheral ring compartmentation in juxtaposition to the steering wheel rim and center compartmentation in overlying juxtaposition to the steering wheel hub. The peripheral ring compartmentation when pressurized provides greater resistance to collapse than the center compartmentation, whereby the peripheral ring compartmentation is adapted to guide the vehicle operator upon contact of the latter with the cushion toward the center compartmentation thereby to maintain the vehicle operator in substantially centered cushioned relationship to the steering wheel assembly under vehicle impact conditions. This air bag contains two compartments; an outer, donut-shaped ring or torus and an inner compartment of somewhat larger volume. This is an example of a bag within a bag where an outer bag is connected to an inner bag by flapper valves.
U.S. Pat. No. 4,964,652 (Karlow) discloses a system for venting excessively high pressure gas incident to deployment of an air bag comprising a diaphragm that is rupturable upon the occurrence of a threshold pressure internally of the air bag to instantaneously release the pressure. This is a pressure relief system through the center of the module.
Japanese Patent No. 89-090412/12 describes fabricated cloths are laminated in layers at different angles to each other""s warp axis to be integrated with each other. Strength and isotropy are improved. The cloth is stated as being useful for automotive air bags for protecting the passenger""s body.
U.S. Pat. No. 5,322,326 (Ohm) describes a small limited protection air bag manufactured in Korea. Although not disclosed in the patent, it appears to use a plastic film air bag material made from polyurethane. It is a small air bag and does not meet the United States standards for occupant protection (FMVSS-208). The film has a uniform thickness and if scaled to the size necessary for meeting U.S. Standards it would likely become of comparable thickness and weight as the current fabric air bags.
Of particular interest, FIG. 6 shows an air bag 33 having a shape that conforms to the human body by forming a two-fold pocket bag. Junction points are provided such that after inflation, the head of a passenger is protected by an inflated part around the upper junction point while the upper part of the passenger is covered with the other inflated part around the middle junction points and a U-shaped junction line. In contrast to pertinent inventions disclosed below, the junction points and lines do not enable the formation of an air bag having a plurality of substantially straight or elongate compartments which can be deploy along the side of a vehicle in order to protect the occupant(s) from injury. Rather, the junction points and lines result in the formation of a limited-use air bag which will conform only to the human body, i.e., having a section for engaging the head and a section for engaging the upper body. Other applications of junction points and lines are not contemplated by Ohm.
U.S. Pat. No. 5,811,506 (Slagel) describes a thermoplastic, elastomeric polyurethane for use in making vehicular air bags. The polyurethane is extrudable so that air bags of various shapes and sizes can be formed therefrom.
A principal object of this invention is to form a tubular air bag from flat sheets of film or composite material, or by blow molding or a similar process in order to create an air bag for use to protect occupants in the event of a crash of the vehicle, which may be substantially larger than current air bags and which may be designed to interact with the occupant regardless of where he/she is positioned without causing significant injury and thereby to improve the protection provided by the air bag. One of the materials for the air bag is chosen from the class of plastic materials known as thermoplastic elastomers which includes, among others, polyurethane, polyester elastomer and metallocene-catalyzed polyolefin. A plastic material is called an elastomer when its elongation prior to failure is large, sometimes as large as 100%, 200%, 400% or more. The driver air bag version uses the inelastic properties of a layer of the film material to cause the air bag to attain the desired shape without requiring the use of tethers. As a driver side air bag, for example, it can be substantially elliptical in two orthogonal planes and circular in a third orthogonal plane. If a composite material composed of film and a net, an inelastic film and an elastic film, or film and a fabric, is used to form a hybrid design, the relatively inelastic properties of the film are used to create the desired flat elliptical shape, for example, while the net, elastic film or fabric is used to provide other desirable features including tear resistance.
Other objects and advantages of this invention, or other disclosed inventions, include:
1. To provide an air bag which can be manufactured without the use of sewing or other manually intensive operations.
2. To provide an air bag which is considerably lighter and smaller, when folded in the inoperative condition, than current fabric air bags.
3. To provide a driver air bag which does not require the use of tethers.
4. To provide an air bag for use on the front passenger side of the vehicle which can be easily manufactured from a minimum number of parts without the use of sewing.
5. To provide a substantially conventional driver fabric air bag which can be manufactured without the use of tethers.
6. To provide an air bag which can be manufactured using a low cost blow molding or similar technology.
7. To provide an air bag which has been optimized to substantially equalize the stresses in the material thereof.
8. To provide an air bag where the material thickness is varied to reduce the stress in the high stress areas of the air bag.
9. To provide an air bag where optimization procedures have been used to substantially eliminate folds and wrinkles in the surface of the inflated air bag.
10. To provide an air bag comprising film where the thickness to diameter ratio is less than 0.7 without the use of tethers and, in some cases, less than 0.6.
11. To provide a very low cost air bag, with respect to the fabrication thereof.
12. To provide a method of manufacturing an air bag permitting any desired shape air bag to the manufactured from flat panels.
13. To provide an air bag where at least one layer is made from a thermoplastic elastomer which is substantially lighter than conventional fabric air bags.
14. To provide an air bag module which is substantially less injurious to out-of-position occupants during air bag deployment.
15. To utilize thin film air bags in a manner which eliminates the catastrophic bursting of the film in the event of an inadvertent puncture.
16. To provide a plastic film air bag where the thickness is varied in a desired pattern, e.g., a pattern of thicker reinforcement sections and spanning sections of thin film.
17. To provide an air bag system which automatically adjusts to the presence of a child seat.
18. To reduce the injury potential to an out-of-position occupant from the deploying air bag.
19. To provide an air bag module utilizing the combination of an air bag made substantially of film and a pyrotechnically opening deployment door.
20. To provide an occupant restraint air bag system for a single occupant which is composed of a plurality of air bags.
21. To provide an air bag system for the protection of an occupant which automatically adjusts to the occupant""s seating position.
22. To provide an air bag system which exhausts back through the inflator structure thereby eliminating the need for vent holes in the air bag.
23. To provide a method of containing a plurality of air bags through the use of a net structure.
24. To provide an air bag system having a variable exit orifice to reduce occupant injury including chest and head maximum accelerations, to reduce the amount of propellant required, and to permit more efficient use of the air bag deflation.
25. To provide a simple construction method for an air bag composed of several air bags.
26. To provide an air bag design which will be available in the event of multiple impacts where the air bag is not fully utilized during the initial impact.
27. To retain the gas in the air bag for a substantial period of time until it is impacted by an occupant.
28. To minimize the total amount of gas and contaminants produced by all of the inflators in the vehicle.
29. To provide an air bag having a plurality of interconnected gas-receiving compartments.
30. To provide an air bag designed to inflate in the passenger compartment alongside the side door of the vehicle.
31. To provide an air bag which provides front to side coverage for a front-seated vehicle occupant which would prevent the occupant from impacting the A-pillar in a crash.
In order to achieve at least some of these objects, an air bag for a vehicle in accordance with the invention comprises a plurality of sections of material joined to one another, e.g., heat-sealed or adhesively-sealed, to form a plurality of substantially straight, interconnected compartments receivable of an inflating medium. The sections of material may be discrete sheets of film with optional tear propagation arresting means. Two or more of the sections of material may be at least partially in opposed relationship to one another and then joined to one another at locations other than at a periphery of any of the sections to thereby form the interconnected compartments between the sections of material. The sections of material may be joined to one another along parallel lines or links to thereby form the straight interconnected compartments between the sections of material, which when inflated, will be tubular.
An inflatable occupant protection system in accordance with the invention includes a housing mounted in the vehicle and having an interior, a deployable inflatable element or air bag contained within the housing interior prior to deployment, inflation means coupled to the housing for inflating the air bag (such as a gas generator for supplying a gas into the interior of the air bag), the air bag being attached to and in fluid communication with the inflation means, and initiation means for initiating the gas generator to supply the gas into the interior of the air bag in response to a crash of the vehicle, i.e., a crash sensor. The air bag may be as described in the paragraph above.
The housing may be elongate and extends substantially along the entire side of the vehicle such that the air bag is arranged to inflate between a side of the vehicle and the respective spaces above both the front and rear seats. In another implementation, the housing is arranged in the front seat and extends between sides of the vehicle such that the air bag is arranged to inflate outward from the front seat toward the rear seat.
Also disclosed is a method for manufacturing an air bag for a vehicle in which a plurality of sections of material are joined together to form a plurality of substantially straight, interconnected compartments, e.g., by applying an adhesive between opposed surfaces of the sections of material to be joined together or heating the sections of material to be joined together. The sections of material may be joined together along parallel lines to form the straight, elongate interconnected compartments which become tubular when inflated with a gas.
Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.
The tear propagation arresting means for the film sheets may be (i) the incorporation of an elastomeric film material, a laminated fabric, or net, which are connected to each of the pieces of plastic film (e.g., the inelastic film which provides the desired shape upon deployment of the air bag), or (ii) means incorporated into the formulation of the plastic film material itself. Also, the two pieces of film may be formed as one integral piece by a blow molding or similar thermal forming process.